ANTI-INFECTIOUS SERUM. 489 



used in testing the genuineness of a suspected Eberth 

 bacillus. A few hundredths of a c.c. of such serum, in- 

 jected into the peritoneal cavity, will protect a guinea-pig 

 against several times the fatal dose of Eberth bacilli, 

 whereas 0.5 c.c. of such serum will not protect against the 

 colon bacillus. 



Typhoid fever. The Eberth bacillus, like the cholera 

 vibrio, colon bacillus, etc., does not give rise to very 

 poisonous soluble products when grown on ordinary bouillon. 

 A soluble toxin has, however, been recently obtained by 

 cultivating the highly virulent germ on an alkaline medium 

 prepared by digesting the spleen with pepsin. With such a 

 toxin Chantemesse has been able to obtain, although with 

 difficulty, an antitoxic serum. 



When, however, living or dead Eberth bacilli are in- 

 jected subcutaneously or intraperitoneally, a condition of 

 immunity is established and the serum in this case is anti- 

 infectious. The method of immunizing the guinea-pig or 

 rabbit is essentially the same as that given above under 

 cholera. The serum of a guinea-pig immunized in this way 

 has about the same preventive action as that of a con- 

 valescent from typhoid fever. The rabbit is more sensitive. 

 The virulence of the Eberth bacilli will vary greatly, thus, 

 some will produce death in a guinea-pig when *V of a loop- 

 ful is injected into the peritoneal cavity. Usually, however, 

 i - a loopful is necessary. 2-3 loopsful of a culture, which 

 has been killed by exposure to chloroform, or to a tempera- 

 ture of 65, will be fatal to a 100 g. guinea-pig in 24 hours. 



The defibrinated blood of an animal that has died of 

 an infectious disease may be employed to confer immunity. 

 Thus, Toussaint injected into sheep 3 c.c. of defibrinated 

 anthrax blood, previously heated to 55 for 10 minutes, and 

 obtained immunity. The heart-blood of rabbits dead of 

 swine-plague, when heated to 54-58, will protect rabbits in 



